Means to suppress radio frequency waves upon the inside of tubular conductors



Oct. 26, 1943. F. TISCHER ETAL MEANS T0 SUPPRESS RADIO FREQUENCY WAVES UPON THE INSIDE OF TUBULAR CONDUCTORS Filed Nov. 50, 1940 Fly. 3

Fig. 4"

ATTORNEY.

Patented Oct. 26, 1943 MEANS T SUPPRESS RADIO FREQUENCY WAVES UPON THE INSIDE OF TUBULAR CONDUCTORS Friedrich Tischer and Hans Jakob namvon Baeyer, Berlin, Germany; vested in the Alien Property Custodian Application November 30, 1940, Serial No. 367,935 In June 21,1939

3 Claims. (Cl. 178-44) A problem which frequently arises in practice is to exclude radio frequency waves of certain frequencies from a line. This problem is diflicult of solution in the case of coaxial or concentric lines, for in the past there has been no other way to accomplish this than to break open the line in order to get at the inner conductor. However, this affects the line constants to a considerable degree. Now, according to the invention, a definite frequency is excluded from a line in a simple way by splitting the outer conductor by providing a narrow slot therein (while 1 the inner conductor is continuous), and to adjoin to the said slot an outwardly extending metallic chamber or space which is externally closed, said chamber being in resonance with the wave to be suppressed. This chamber or hollow space may be likened to the so-called "suppressor pots" or traps heretofore mounted on the outer surface of conductors to the end of suppressing waves on the outer surface. Con. tradistinct therefrom, the outer surface is here practically unaffected (save for a small bulge), while the trap is inserted in the inside surface.

An exemplified embodiment of the invention is illustrated in Figure 1 of the appended drawing, while Figures 2 to 5 illustrate modifications thereof. Figure 1 illustrates a shielded line L, the outer conductor C of which has a slot S to which is connected an outwardly extending tuned chamber or hollow space formed by a single layer toroid T. The capacity between'the edges of slot S and the inductance of toroid T ment which is particularly advantageous for the reason that the pot or trap is composed of two terminations of parts of line L1 and L2 having flanges F which are simply screwed together on the outside by bolts B. The two ends of the inner conductor 11 and I2, for instance, may be united by socket-and-plug arrangement P. In this way the trap or pot constitutes at the same time a coupling bush or box for a shielded radio frequency cable. A similar exemplified embodiment is shown in Figure 3. In this form of construction the trap or pot part united with conductor L1 is screwed together with the other trap part by means of a screw-thread G. If the screwed portions are made sufllciently long, the trap may be thereby tuned, if desired. Of course, other ways and means adapted to insure tuning and to build the trap are contemplated as being within the scope of the invention.

Figure 4 shows, finally, a simpler embodiment in which there is attached to a slot of the outer conductor 0 a tubular line T having a length equal to A/4 and short-circuited at the ends. This embodiment has the same effect as the traps hereinbefore described. What is essential in the'invention is that the inner surface of the outer conductor is broken open only by a narrow slot; in other words, that such waves as have a frequency other than the resonance frequency of the trap and for which the latter does not constitute a high impedance, are able to flow through the line without being in any way affected. The form of the external hollow body or chamber adjoining and connected with the slot is practically immaterial. For instance, this body may be formed so as to be adapted to other requirements; for instance, as above pointed out, it could serve as a coupling sleeve or serve to support the entire line, etc. If more than one frequency is to be excluded and suppressed, then a series of traps tuned to different waves may be arranged in sequence. It will be understood that it is, of course, also possible to aifect the tuning of the trap by means of material of suitable dielectric constant, permeability,

, and suitable phase angle difference.

As can be seen from Figure 5 the stopper or suppressor means could be mounted also at the end of a line, say, where it adjoins an antenna A. Otherwise, the structure of Figure 5 is similar to that of Figure 3.

We claim:

1. A joint for connecting a pair of adjacent ends of tubular conductors, each of said ends having exteriorly recurrent portions, each of said recurrent portions being surrounded by a short conductive tube coaxially arranged with respect thereto, said tubes being connected together at their adjacent ends and connected to said. tubular conductors at their remote ends, the spacing between the most closely adjacent portions of said tubular conductors being such that the capacity therebetween is so related to the interior conducting path from one such portion to the other as to be resonant to waves of a frequency to be blocked from passage along the interior of said tubular conductors.

2. A joint for connecting a pair of adjacent ends of tubular conductors, each of said ends having exteriorly recurrent portions, each of said recurrent portions beingsurrounded by a short conductive tube coaxially arranged with respect thereto, said tubes being connected together at their adjacent ends and connected to said tubular conductors at their remote ends, the spacing between the most closely adjacent portions of said tubular conductors being such that the capacity therebetween is so related to the interior conducting path from one such portion to the other as to be resonant to waves of a frequency to be blocked from passage along the interior of said tubular conductors, the adjacent ends of said short conductive tubes being provided with flanges whereby said tubes are connected together. w 3. A joint for connecting a pair of adjacent ends of tubular conductors, each of said ends having exteriorly recurrent portions, each of said recurrent portions being surrounded by a short conductive tube coaxially arranged with respect thereto, said tubes being connected together at their adjacent ends and connected to said tubular conductors at their remote ends, the

spacing between the most closely adjacent portions of said tubular conductors being such that the capacity therebetween is so related to the interior conducting path from one such portion to the other as to be resonant to waves of a frequency to be blocked from passage along the interior of said tubular conductors, the adjacent ends of said short conductive tubes being provided with flanges and means for clamping said flanges together.

HANS JAKOB RIT'IER VON BAEYER. FRIEDRICH TISCHER. 

